tbc: fix SMSG_MAIL_LIST_RESULT parsing for TBC 2.4.3

TBC 2.4.3 differs from WotLK in four ways:
- Header: uint8 count only (WotLK: uint32 totalCount + uint8 shownCount),
  so the WotLK parser was reading 4 garbage bytes before the count
- No extra unknown uint32 between itemTextId and stationery in each entry
- Attachment item GUID: full uint64 (WotLK uses uint32 low GUID)
- Attachment enchants: 7 × uint32 id only (WotLK: 7 × {id+duration+charges})

The resulting mis-parse would scramble subject/money/cod/flags for every
mail entry and corrupt all attachment reads.  Add TbcPacketParsers::parseMailList
with the correct TBC 2.4.3 format.

include/game/packet_parsers.hpp

@@ -295,6 +295,9 @@ public:
     bool parseMonsterMove(network::Packet& packet, MonsterMoveData& data) override;
     // TBC 2.4.3 SMSG_GOSSIP_MESSAGE quests lack questFlags(u32)+isRepeatable(u8) (WotLK added them)
     bool parseGossipMessage(network::Packet& packet, GossipMessageData& data) override;
+    // TBC 2.4.3 SMSG_MAIL_LIST_RESULT: uint8 count (not uint32+uint8), no body field,
+    // attachment uses uint64 itemGuid (not uint32), enchants are 7×u32 id-only (not 7×{id+dur+charges})
+    bool parseMailList(network::Packet& packet, std::vector<MailMessage>& inbox) override;
 };
 
 /**